Not Applicable.
Currently, many automotive bumper beams are roll formed from high strength steel. These beams are roll formed and seam-welded to create a closed section bumper beam that is an efficient light weight structure. The limitations of the roll form process permit only a constant cross-sectional shape, and the limits of high strength steel permits only limited plan view sweep (curvature) being formed into the beams. For rear bumper beams, where a straight or small sweep beam is required, a roll formed high strength beam is well suited. For front end vehicle applications, where the current styling trends require large plan view sweep, however, the roll formed section cannot follow the sweep of the fascia. This results in filling the excess space between the beam and fascia with absorber foam, or utilizing an extruded aluminum or stamped beam. An extruded aluminum beam has higher sweep capability, but is more expensive. Both extruded aluminum and roll formed beams have the disadvantage of a constant cross-sectional shape. This forces the bumper designer to utilize the maximum strength cross section throughout the length of the bumper, although it is not required along the entire length and is typically only required at the center.
Thus, one may easily see the need to provide a high strength bumper beam that has high sweep capability and the capability to vary the cross section depth. This will permit use of high strength steel in a tailored cross section. The result will be an extremely efficient, light weight structure that will allow secondary cost savings by eliminating unnecessary absorber and fascia package space.
The approach to this task is to create two ultra high-strength, shallow, open C-sections, by roll forming or press braking, and sweeping them individually. The two sections are welded to transverse support members, such as xe2x80x9cbulkhead platesxe2x80x9d, between the c-section assembly to form a bumper beam structure. The bulkhead plates can be corrugated to provide beam crush during a high speed vehicle crash. This is desirable to provide additional energy absorption and crush space. A second alternative is to incorporate energy absorbing structures, such as injection molded cones, or deformable solids, for example, between the C-Sections to absorb additional energy during a high speed crash when the C-Sections will be crushed.
The sweeping of the shallow open sections can be more easily accomplished than sweeping a deep closed section. This permits use of even higher strength steels, including materials that have a yield strength of about two hundred twenty thousand pounds per square inch (220 kips) or other metals and composite materials. Each C-section can be swept to a different sweep to create a variable cross section depth beam when the two are assembled to form the final beam. The variable cross section permits tailored bending stiffness along the length of the beam and results in less material usage, lower mass, and lower cost than a constant section beam.
The structural concept of the double C-section also has application to other beam applications, including side door guard beams, for example. Many design variations of the bulkheads are also, possible. They could be simple plates, corrugated, plates with end flanges, a W-section, or serpentine section, for example. A main function of the bulkheads is to weld the front and rear C-sections together. Variations in the design of the front and rear sections are also possible, and are covered within the spirit of this disclosure.
A secondary function of the bulkheads is to provide additional energy absorption during high speed impact and crush of the vehicle front end. Variations in the design of internal, deformable bulkheads, incorporating crush energy absorbers including plastic cells, foam, epoxy composite, ceramic forms, are possible and are covered with the spirit of this disclosure.
These and other features, objects, and benefits of the invention will be recognized by one having ordinary skill in the art and by those who practice the invention, from the specification, the claims, and the drawing figures.
FIG. 1 is a fragmentary longitudinal perspective view of a bumper assembly according to the invention;
FIG. 2 is a bottom plan view thereof;
FIG. 3 is a fragmentary longitudinal perspective view of two open sided beam members assembled into a beam according to the invention;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a cross-sectional view of an open sided beam member used in the invention;
FIG. 6 is the view of FIG. 3, showing optional tie plates between the channel members;
FIG. 7 is the view of FIG. 4, showing alternative tie plates between the channel members;
FIG. 8 is a fragmentary top plan view of a beam according to the invention, showing a corrugated bulkhead with fastening flanges;
FIG. 9 is a fragmentary top plan view of a beam according to the invention, showing a serpentine bulkhead with fastening flanges; and
FIG. 10 is a fragmentary longitudinal perspective view of two open sided beam members positioned as they would be assembled into a beam according to the invention, showing an alternative cross section for the channel members; and
FIG. 11 is a front longitudinal perspective view of a first alternative bumper assembly according to the invention;
FIG. 12 is a top plan view thereof;
FIG. 13 is a front elevational view thereof,
FIG. 14 is a cross-sectional view thereof along line XIVxe2x80x94XIV of FIG. 13;
FIG. 15 is a cross-sectional view thereof along line XVxe2x80x94XV of FIG. 13;
FIG. 16 is a cross-sectional view thereof along line XVIxe2x80x94XVI of FIG. 13; and
FIG. 17 is an end elevational view thereof.